This invention relates to the provision of local telephone services.
The telecommunications industry is currently undergoing a transformation from a traditional circuit switched based PSTN network, which was originally designed and optimized for carrying voice telephony traffic, to packet based networks which will be capable of efficiently supporting both voice and data communications. A next generation network (NGN) is a packet-based network that employs new control, management, and signaling techniques to provide both narrow-band voice telephony services and broadband, multimedia services. NGNs are able to satisfy a user""s need for higher bandwidth while allowing service providers to offer innovative services, enabling new services and revenue streams, and reducing management costs and time to market.
A generalized local service provider NGN architecture is shown in FIG. 1. It consists of two subnetworks, a public switched telephone network (PSTN) and an integrated voice and data packet network, which comprises access network 104 and a backbone network 106. The access packet network 104 physically connects subscribers 120 to the local service provider network. In the case of residential customers, the access network 104 will typically be based on digital subscriber loop (xDSL) technology deployed in the local loop or MSCNS DOCSIS technology deployed over coax cable. On the customer side, the access network terminates on the customer premises device, which is called here the access gateway 108. The particular implementation of an access gateway depends on the technology utilized in the access network. For access networks utilizing xDSL technology, the access network 108 may include an xDSL modem. For a hybrid fiber-coax based access, the access gateway 108 may be merged with set top boxes traditionally utilized for receiving TV signals broadcasted from cable-based distribution plants. Traditional telephone sets are either directly connected to the access gateway 108 or they are connected via a more elaborate home area network.
The packet based backbone network 106 is optimized for efficiently transmitting large amounts of data and typically utilizes IP, ATM and/or SONET technologies. For example, in the initial network deployment stages, the access and backbone networks could utilize ATM technology. However, since ATM switched virtual circuit (SVC) technology is not mature and ubiquitous enough to deploy end-to-end in the packet network, private virtual circuits (PVCs) are used in the access network and, frequently, in the backbone network.
The access network 104 is connected to the backbone network 106 via backbone gateways 110, which bridge transport technologies utilized in the two networks. For example, in the case of a xDSL based access network the backbone gateway 110 includes digital subscriber loop access multiplexer (DSLAM) functionality. Calls spanning the packet network and PSTN network, such as calls originating from access gateways 108 and terminating on the PSTN or vice versa, are routed through trunking gateways 112. A signaling gateway 114 is responsible for receiving signaling information from the PSTN (e.g., signaling system 7 packets) and routing that information to the appropriate network elements in the NGN. The signaling gateway can be a separate component or can be integrated into a service manager (SM) 116.
The NGN has its own control infrastructure. Typically, network elements are designated to support service, session and connection signaling. In this document, these elements are called service managers (SMs) but depending on the protocols involved, these elements are also called media gateway controllers, call agents, gatekeepers, and signaling agents.
Local service providers have started the transition of their networks from the traditional PSTN infrastructure to an NGN architecture to offer both local and long distance services. The challenge for the NGN network equipment vendors will be to support graceful transition of the current local service subscribers to the new infrastructure.
A serious limitation of the NGN architecture of FIG. 1 is that it does not support graceful migration of local services from the existing circuit switched infrastructure to the NGN network. In this architecture, the NGN network must provide all local services for phones utilizing packetized voice in the local loop. In addition, once a particular line is provisioned to receive local services from NGN, there is no easy and inexpensive way of re-provisioning the line to utilize PSTN local services.
Furthermore implementing within the NGN network all of the local services that are currently available in the PSTN is not a trivial task. Class 5 switches providing local PSTN services have been evolving for decades and by some estimates currently support over 500 different local service features. It is not reasonable to expect that all these features will be totally replicated in the new NGN infrastructure within a short timeframe. However, if NGN supports only a small subset of the local features then the deployment of the NGN may be limited to a small number of very specific target customers. Success of the NGN deployment will then depend on the reliability of the prognosis that can be made for defining a limited set of features to satisfy the needs of targeted customers until the NGN network matures. These deployment limitations could hamper the growth of the NGN network.
Prior techniques to address the migration of PSTN to NGN have certain limitations. FIG. 2 illustrates a specific implementation of the general NGN architecture depicted in FIG. 1. In this xDSL-based architecture, local service features for some telephones 222 are implemented by a class 5 end office switch 218. For other telephones 220, local service features are implemented based on the NGN service control infrastructure (i.e. based on the SM 216 network component).
For each set of telephone lines multiplexed over a single xDSL equipped local loop, the phone 222 utilizing analog transmission uses the bottom 4 kHz of the frequency spectrum of the access loop. The media stream for this line is separated in the DSLAM 209 and connected to the line side of the class 5 switch 218 which is connected to a tandem switch 224 in the PSTN 200. For the remaining phones 220, voice communication is implemented by transmitting packetized voice stream over the upper portion of the frequency spectrum. The packetized voice stream is routed via the DSLAM 209 and the network gateways 211 which are connected to the backbone packet network 206. The SM 216 controls local service features for telephones utilizing packetized voice.
While a limited number of lines are able to access local services provided by a class 5 switch in this architecture, these lines are unable to access any innovative features provided by the NGN. In addition, no easy or cost effective way exists to re-provision a line for a packetized voice customer who wishes to utilize services offered only on a class 5 switch.
FIG. 3a illustrates a network architecture that provides users access to class 5 switch features and an NGN architecture for transport. Phones 322 use traditional local loop facilities to connect to a class 5 switch 318. In this architecture, the class 5 switch 318 connects to an NGN network 303 via a packet data interface 319 located at the switch 318. While this architecture provides a service provider with access to some of the bandwidth and cost reduction benefits of the NGN, customers are not able to access innovative features offered by the NGN.
This architecture is sometimes modified to include packetized local loops as illustrated FIG. 3b. Virtual phones 320 use packetized local loop facilities (e.g., DSL) to connect to a local loop gateway 309. The packetized local loop network communicates with a class 5 switch 318 using traditional local loop signaling (e.g., channel associated signaling) through a local loop gateway 309. In this architecture, the class 5 switch 318 connects to an NGN network 303 via a packet data interface 319 located at the switch 318. This architecture has the benefit of providing multiple virtual phone lines over a single physical line. However, customers are not able to access the innovative features offered by the NGN.
An objective of my invention is to provide a network architecture that will allow local service providers to gracefully migrate local service features to the NGN network. This will include providing ability to efficiently switch local lines from the NGN to PSTN local service infrastructures and vice-versa.
It is yet another objective of my invention to enable supporting network infrastructure transparency to service subscribers and to reduce the local service provider""s risk associated with abruptly replacing one network infrastructure with another.
My invention is directed to a system which allows providers of packet based networks such as NGNs to offer customers the choice of local services provided by switches in the PSTN or services provided by an SM in the NGN. In a specific embodiment of my invention, the system includes an access gateway providing analog or digital access to the NGN, an SM identifying selected mode of operation for the customer and providing control of local services offered by the NGN, a subscriber database storing customer service preferences, a network gateway providing an interface between the NGN and the PSTN, a class 5 end office including digital loop carrier support, and PSTN access tandem switches. The system can operate in two separate modes simultaneously.
In the first mode of operation, the NGN simulates a digital local loop to allow local services to be offered to NGN customers by class 5 switching systems. In this mode, the NGN is transparent to both the customer and the class 5 switching system. This mode of operation is referred to herein as virtual local loop (VLL) mode. In this mode, the SM is notified of a call origination or call termination event. The SM accesses the subscriber database to determine whether the customer subscribes to services offered through the NGN or through the class 5 switch. If the customer subscribes to services offered through the class 5 switch, the packet based network under control of the SM establishes a connection between the network customer and the network gateway through an access gateway. A connection is also established between the network gateway and the class 5 switch. After these connections are established, local loop supervision information is signaled between the packet based network and the class 5 switch using digital loop carrier channel associated signaling. The customer is then connected via the virtual local loop to the class 5 end office which acts as an originating end office for the customer""s line.
Alternatively, the VLL mode of operation could be implemented in another manner. In this implementation, the local loop supervision information is signaled via a combination of channel associated signaling and out-of-band signaling. In this mode, the loop supervision signaling between the class 5 switch and network gateway is via channel associated signaling. The signaling between the network gateway and the SM and between the SM and access gateway is via out-of-band signaling. In this mode, the network gateway translates the channel associated signaling into out-of-band signaling messages.
In a second mode of operation, the NGN simulates a local loop to allow local services to be offered to NGN customers through the SM in the NGN. In this embodiment, the NGN is transparent to the customer. This mode of operation is referred to herein as native NGN mode.
The access gateway is continually monitoring to detect a call origination event on a customer""s line. When a call event is detected for the customer""s line, the access gateway sends a message reporting the event to the SM.
Based on the information in the subscription database, the SM determines that the customer has selected service features offered through the SM and the call should be established in native NGN mode. In native NGN mode, the SM sends a message to the access gateway requesting that the gateway provide dial tone and collect the dialed digits according to the dialed plan specified in the message. The access gateway provides a dial tone, collects the dialed digits and reports the dialed number to the SM and the SM immediately acknowledges that notification. The call to the dialed number is then established.